The present invention relates to video quality measurements, and more particularly to an instrument for real-time video quality measurements which automatically measures video quality and monitors and logs when selected video clips have been received.
Modern digital video systems may introduce distortions into a video image via a number of different means, such as compression, transcoding, transmission errors, analog distortions, etc. In order to measure the quality of the video at the picture level, i.e., the quality of the final decoded picture, it is necessary to either:                perform subjective testing using human operators who determine video quality of the pass/fail status of a device,        use a single-ended video measurement device, such as the Tektronix PQM300 Picture Quality Monitor which does not accurately detect many types of errors as it does not use a reference sequence, or        measure the video off-line using a video quality measurement device, such as the Tektronix PQA300 Picture Quality Analyzer (see U.S. Pat. No. 5,818,520) which has many restrictions including a limited sequence length, modification of video content to achieve alignment, and non-realtime operation.In many applications the video content cannot be restricted or modified in any way in order to achieve alignment. The quality measurement device needs to be able to rapidly drop in and out of alignment as the test video content changes, and needs to perform measurements to produce error maps, graphs or pass/fail decisions in real-time. None of the current alternatives offers an adequate solution to this problem, so human operators are still typically used to perform the quality measurement task. This is not desirable since it is known that the results achieved by human operators are not objective or repeatable, are prone to error, and are expensive.        
What is desired is a video quality measurement instrument that accepts any video content, does not modify the video content, rapidly achieves temporal and spatial alignment when test video matches reference video, rapidly drops out of alignment once test video fails to match reference video, works with very long sequences, enables a programmable video quality measurement including setting pass/fail thresholds, selecting regions of interest for computing quality and measuring different channels, logs all results and keeps a record of when a particular reference clip is played so that the user may keep track of both the time, frequency and quality at which a particular clip was shown, allows both single-input operation and double-input operation, and operates in real-time.